Mammographic Density, Body Mass Index, and Dietary Habits in Japan and Hawaii

Abstract

The topic of this master's thesis is breast cancer risk and its relationships to one's diet and nutrition. There is evidence that lifestyle, family history, dietary habits, reproductive history, and anthropometric characteristics are associated with the risk of breast cancer. The well-established risk factors for breast cancer are age, reproductive behavior, family history of breast cancer, years of education, and anthropometric and dietary factors. However, when it comes to dietary factors, there needs to be further research to clarify the relationship with the disease. Breast cancer incidence rates differ by ethnicity and also by geographic location. Migrant studies have shown that rates among migrants from a low-risk country to a high-risk country were higher than the rates among women in their homelands. This suggests that the increase in rates among the same ethnic group might be caused by changes in the environment, including dietary habits. The objective of this study was to investigate the association of diet with Body Mass Index (BMI) and breast cancer risk, as measured by mammographic density, among Japanese women in Japan and Japanese and Caucasian women in Hawaiʻi. The validated Food frequency questionnaires (FFQ) were used to assess dietary intake as well as descriptive characteristics, which include demographic, anthropometric and reproductive characteristics. Analysis of Variance was used to compare the differences in descriptive characteristics and diet among the three groups of women. To explore the association between diet and the determinants of BMI and mammographic density, multiple regression was applied. Among the three groups of women in the study, anthropometric and mammographic characteristics differed by ethnicity but not by place of residence. Dietary habits differed considerably by ethnicity and place of residence. It appeared that the diet of Japanese women in Hawaiʻi was a combination of foods eaten in Japan and dietary habits of Caucasian women in Hawaiʻi. Intake of ethanol was associated with BMI in both pre- and postmenopausal women, while association with the other dietary factors differed depending on menopausal status. BMI was more strongly associated with dietary variables among premenopausal women than descriptive characteristics, while it was strongly associated with Japanese ethnicity among postmenopausal women. Intakes of fat, cholesterol, carbohydrates, vitamin A, fish, and eggs were associated with mammographic density in the current study. BMI was the strongest predictor of mammographic density. Dietary intake explained little of the variation in mammographic density. It is still questionable whether mammographic density among different ethnic groups is comparable as an indicator for breast cancer risk. Total dense area of the breast maybe a better indicator. For future studies, it is suggested that associations between body fat distributions, as a possible indicator for breast cancer risk, and diet be examined, adjusted for reproductive histories and biochemical measures for hormones.